The present invention relates generally to semiconductor fabrication and, more particularly, to methods for preparing semiconductor wafers in which preparation operations are performed on a vertically oriented wafer. The preparation is configured to take place in a single enclosure apparatus.
In the fabrication of semiconductor devices, a variety of wafer preparation operations are performed. By way of example, these wafer preparation operations include cleaning operations and polishing/planarization operations, e.g., chemical mechanical planarization (CMP). One known polishing/planarization technique uses platens with planetary polishing motion. One disadvantage of this technique is that it requires multi-step procedures, which are time-consuming and relatively expensive. Another disadvantage of this technique is that it tends to produce wafers having surfaces that suffer from a relatively high degree of topographic variations.
Another known polishing/planarization technique involves circumferential polishing. In one known circumferential polishing system, a wafer is rotated in a vertical orientation by wafer drive rollers. As the wafer is rotated, a pair of cylindrical polishing pads is brought into contact with the opposing surfaces of the wafer. The polishing pads are mounted on counter-rotating mandrels disposed on opposite sides of the wafer being processed. The mandrels span across the diameter of the wafer so as to pass over the wafer center. The rotation of the mandrels causes a rotary pad motion perpendicular to the wafer diameter in a circumferential direction. During the polishing operation, nozzles direct sprays of liquid, e.g., an abrasive slurry, a chemical solution, or a rinse solution, on the opposing surfaces of the wafer.
One drawback of this known circumferential polishing system is that it provides only circumferential polishing motion. As such, the relative velocity of each pad is not uniform across each wafer surface, with the velocity near the wafer edge being greater than the velocity near the wafer center. This is problematic because it not only results in the creation of circumferential residual scratches on each of wafer surfaces, but also results in a more wafer material being removed from the center portion of the wafer than near the perimeter due to the greater dwell time experienced by the center portion of the wafer. As a consequence of this nonuniform material removal rate, each of the opposing surfaces of the wafer tends to have a flared contour, i.e., a contour in which the central portion is depressed relative to the edge portions. As the semiconductor industry moves toward the use of smaller, e.g., 0.18 .mu.m and smaller, feature sizes, such flared contours are undesirable.
In view of the foregoing, there is a need for a method and apparatus for circumferential wafer preparation that minimizes the creation of circumferential residual scratches, provides processed wafers have desired surface contours, and enables multiple wafer preparation operations to be performed on a wafer without moving the wafer between stations.
Broadly speaking, the present invention fills this need by providing apparatus for preparing wafers.
In accordance with one aspect of the present invention, an apparatus for preparing a semiconductor wafer is provided. The apparatus includes a pair of drive rollers disposed so as to support a semiconductor wafer in a substantially vertical orientation. Each of the drive rollers is configured to be coupled to a drive belt for rotating the drive rollers. The apparatus further includes a pair of wafer preparation assemblies that is movably disposed in an opposing relationship. Each of the wafer preparation assemblies have a first wafer preparation member and a second wafer preparation member. The wafer preparation assemblies being movable into a first position in which each of the first wafer preparation members is positioned to perform a first wafer preparation operation on the wafer and into a second position in which each of the second wafer preparation members is positioned to perform a second wafer preparation operation on the wafer.
In accordance with another aspect of the present invention, an apparatus for polishing a semiconductor wafer is disclosed. The Apparatus includes a pair of drive rollers disposed so as to support a semiconductor wafer in a substantially vertical orientation. Each of the drive rollers is configured to be coupled to a drive belt for rotating the drive rollers. The apparatus further includes a pair of wafer preparation assemblies movably disposed in an opposing relationship, and each of the wafer preparation assemblies having a cylindrical upper mandrel having a polishing pad affixed thereto and a cylindrical lower mandrel having a polishing pad affixed thereto. The wafer preparation assemblies being movable into a first position in which each of the upper mandrels is positioned to perform a first polishing operation on the wafer and into a second position in which each of the lower mandrels is positioned to perform a second polishing operation on the wafer.
In yet another aspect of the invention, an apparatus for preparing a semiconductor wafer disclosed. The apparatus includes a housing and a pair of drive rollers disposed within the housing so as to support a semiconductor wafer in a substantially vertical orientation. Each of the drive rollers is configured to be coupled to a drive belt for rotating the drive rollers. An alignment roller for maintaining the wafer in alignment is also provided. The alignment roller is disposed within the housing above the drive rollers. A pair of wafer preparation assemblies is pivotably disposed within the housing in an opposing relationship, and each of the wafer preparation assemblies have a first wafer preparation member, a second wafer preparation member, a drive assembly for rotating the first and second wafer preparation members, and a pivot shaft. The wafer preparation assemblies being pivotable into a first position in which each of the first wafer preparation members is positioned to perform a first wafer preparation operation on the wafer, into a neutral position in which each of the wafer preparation members is positioned for loading or unloading the wafer, and into a second position in which each of the second wafer preparation members is positioned to perform a second wafer preparation operation on the wafer by rotating the pivot shafts.
It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.